U.S. Pat. No. 5,207,189 discloses a cooling system for an internal combustion engine that eliminates stagnation of a coolant flowing in a plurality of annular passages formed between a cylinder block and a cylinder liner. Inflow and outflow passages are provided in the annular passages and extend in a direction of an axis of the cylinder liner. An inlet passage supplies a coolant to the inflow passage. A guiding member is provided at an entrance of each of the annular passages so as to lead a portion of a coolant to an upstream side of each of the annular passages. A sufficient amount of coolant flows through the annular passages of the cylinder liner, and thus the wall of the cylinder liner can be cooled efficiently.
U.S. Pat. No. 8,402,930 discloses a cooling system for a marine engine having various cooling channels and passages which allow the rates of flow of its internal streams of water to be preselected so that heat can be advantageously removed at varying rates for different portions of the engine. In addition, the direction of flow of cooling water through the various passages assists in the removal of heat from different portions of the engine at different rates so that overheating can be avoided in certain areas, such as the exhaust manifold and cylinder head, while overcooling is avoided in other areas, such as the engine block.
U.S. Pat. No. 8,474,418 discloses a passage separating member positioned in an axial direction of cylinder bores and causing a spacer to contact a bottom surface of a water jacket. When the separating member is inserted in the water jacket, the width of the separating member is reduced due to elastic deformation, so that the separating member can be arranged in the water jacket. After being arranged, the separating member tightly contacts the inner surface of the water jacket due to elastic restoration force. The tight contact prevents the separating member from moving upward in the water jacket. As a result, coolant is prevented from moving between the upper portion and the lower portion with respect to the separating member. The advantages of separate cooling of the coolant in the upper and lower portions with respect to the separating member are obtained. This reliably reduces the temperature difference along the axial direction of the cylinder bore forming body.
U.S. Pat. No. 8,763,568 discloses a spacer fitted inside a water jacket of a cylinder block in an internal combustion engine. The spacer is set so that a space formed between an inner peripheral surface of the spacer and an inner wall surface of the water jacket is smaller than a space formed between an outer peripheral surface of the spacer and an outer wall surface of the water jacket. Accordingly, even if the spacer is shifted in a radial direction, the inner peripheral surface of the spacer comes into abutment on the inner wall surface of the water jacket. Thereby, abutment of the outer peripheral surface of the spacer on the outer wall surface of the water jacket is prevented completely. Therefore, hitting sounds of pistons can be blocked by the space between the outer peripheral surface of the spacer and the outer wall surface of the water jacket.